Lettuce variety 41-342 rz

ABSTRACT

The present invention relates to a  Lactuca sativa  seed designated 41-342 RZ, which exhibits a combination of traits including resistance to downy mildew ( Bremia lactucae ) races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25, Bl:28-Bl:30, resistance to currant-lettuce aphid ( Nasonovia ribisnigri ) biotype Nr:0, resistance to Lettuce Mosaic Virus (LMV) race LMV:1, as well as very thick mature leaves and a small head size. The present invention also relates to a  Lactuca sativa  plant produced by growing the 41-342 RZ seed. The invention further relates to methods for producing the lettuce cultivar, represented by lettuce variety 41-342 RZ.

RELATED APPLICATIONS AND INCORPORATION BY REFERENCE

This application claims priority to U.S. provisional patent applicationSer. No. 62/162,925, filed on May 18, 2015.

The foregoing application, and all documents cited therein or duringtheir prosecution (“appln cited documents”) and all documents cited orreferenced in the appln cited documents, and all documents cited orreferenced herein (“herein cited documents”), and all documents cited orreferenced in herein cited documents, together with any manufacturer'sinstructions, descriptions, product specifications, and product sheetsfor any products mentioned herein or in any document incorporated byreference herein, are hereby incorporated herein by reference, and maybe employed in the practice of the invention. More specifically, allreferenced documents are incorporated by reference to the same extent asif each individual document was specifically and individually indicatedto be incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a new lettuce (Lactuca sativa) varietywhich may exhibit a combination of traits including resistance to downymildew (Bremia lactucae) races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22,Bl:24, Bl:25, Bl:28-Bl:30, resistance to currant-lettuce aphid(Nasonovia ribisnigri) biotype Nr:0, resistance to Lettuce Mosaic Virus(LMV) race LMV:1, as well as very thick mature leaves and a small headsize.

BACKGROUND OF THE INVENTION

All cultivated forms of lettuce belong to the highly polymorphicspecies, Lactuca sativa, which is grown for its edible head and leaves.As a crop, lettuces are grown commercially wherever environmentalconditions permit the production of an economically viable yield.

Lactuca sativa is in the Cichoreae tribe of the Asteraceae (Compositae)family. Lettuce is related to chicory, sunflower, aster, scorzonera,dandelion, artichoke and chrysanthemum. Sativa is one of about 300species in the genus Lactuca.

Lettuce cultivars are susceptible to a number of pests and diseases suchas downy mildew (Bremia lactucae). Every year this disease leads tomillions of dollars of lost lettuce crop throughout the world. Downymildew (Bremia lactucae) is highly destructive on lettuce grown atrelatively low temperature and high humidity. Downy mildew is caused bya fungus, Bremia lactucae, which can be one of the following strains:NL1, NL2, NL4, NL5, NL6, NL7, NL10, NL 12, NL13, NL 14, NL 15, NL16,Bl:17, Bl:18, Bl:20, Bl:21, Bl:22, Bl:23, Bl:24, Bl:25, Bl:26, Bl:27,Bl:28, Bl:29, Bl:30, Bl:31 (Van Ettekoven, K. et al., “Identificationand denomination of ‘new’ races of Bremia lactucae,” In: Lebeda, A. andKristkova, E (eds.), Eucarpia Leafy Vegetables, 1999, PalackyUniversity, Olomouc, Czech Republic, pp. 171-175; Van der Arend et al.“Identification and denomination of “new” races of Bremia lactucae inEurope by IBEB until 2002.” In: Van Hintum, Th et al. (eds.), EucarpiaLeafy Vegetables Conference 2003, Centre for Genetic Resources,Wageningen, The Netherlands, p. 151; Plantum NL (Dutch association forbreeding, tissue culture, production and trade of seeds and youngplants), Van der Arend et al. “Identification and denomination of “new”races of Bremia lactucae in Europe by IBEB until 2002.” In: Van Hintum,Th et al. (eds.), Eucarpia Leafy Vegetables Conference 2003, Centre forGenetic Resources, Wageningen, The Netherlands, p. 151; Plantum NL(Dutch association for breeding, tissue culture, production and trade ofseeds and young plants); IBEB press release “New race of Bremia lactucaeBl:27 identified and nominated”, May 2010; Plantum NL (Dutch associationfor breeding, tissue culture, production and trade of seeds and youngplants), “New race of Bremia lactucae Bl:28 identified and nominated”,March 2011; Plantum NL (Dutch association for breeding, tissue culture,production and trade of seeds and young plants), IBEB press release,“New races of Bremia lactucae, Bl:29, Bl:30 and Bl:31 identified andnominated”, August 2013), Ca-I, Ca-IIA, Ca-IIB, Ca-III, Ca-IV(Schettini, T. M., Legg, E. J., Michelmore, R. W., 1991. Insensitivityto metalaxyl in California populations of Bremia lactucae and resistanceof California lettuce cultivars to downy mildew. Phytopathology 81(1).p. 64-70), and Ca-V, Ca-VI, Ca-VII, Ca-VIII (Michelmore R. & Ochoa. O.“Breeding Crisphead Lettuce.” In: California Lettuce Research Board,Annual Report 2005-2006, 2006, Salinas, Calif., pp. 55-68).

Downy mildew causes pale, angular, yellow areas bounded by veins on theupper leaf surfaces. Sporulation occurs on the opposite surface of theleaves. The lesions eventually turn brown, and they may enlarge andcoalesce. These symptoms typically occur first on the lower leaves ofthe lettuce, but under ideal conditions may move into the upper leavesof the head. When the fungus progresses to this degree, the head cannotbe harvested. Less severe damage requires the removal of more leavesthan usual, especially when the lettuce reaches its final destination.

Of the various species of aphids that feed on lettuce, thecurrant-lettuce aphid (Nasonovia ribisnigri) is the most destructivespecies because it feeds both on the leaves of the lettuce as well asthe heart of the lettuce, making it difficult to control withconventional insecticides. The lettuce aphid feeds by sucking sap fromthe lettuce leaves. Although direct damage to the lettuce may belimited, its infestation has serious consequences because the presenceof aphids makes lettuce unacceptable to consumers.

Lettuce mosaic virus (LMV) mainly infects lettuce seeds, which is theprimary way that the virus is introduced to lettuce in the fields, butalso can infect numerous crops and weeds, thereby creating reservoirs ofthe virus. LMV also can be vectored by aphids, which spread the viruswithin a lettuce field and introduce it into lettuce fields frominfected weeds and crops outside the field.

Symptoms of LMV vary greatly. Leaves of plants that are infected at ayoung stage are stunted, deformed and (in some varieties) show a mosaicor mottling pattern. Such plants rarely grow to full size; head lettucevarieties infected early fail to form heads. Plants that are infectedlater in the growth cycle show a different set of symptoms. These plantsmay reach full size, but the older outer leaves turn yellow, twisted,and otherwise are deformed. On head lettuce, the wrapper leaves oftenwill curve back away from the head and developing heads may be deformed.In some cases, brown necrotic flecks occur on the wrapper leaves.

Cos/Romaine lettuce should provide a product at harvestable stage, whichis accepted by the processing industry and/or consumers. Therefore theharvestable product should not have tipburn, and it should have thick,strongly blistered leaves with a dark green outer leaf color. Further itshould be sufficiently headed, and as a result of this heading providesufficient yellow-colored heartleaves.

Cos lettuce should provide a product at harvestable stage, which isacceptable to the processing industry and/or consumers. Cos lettuce isbrought to the market in the form of wholehead, hearts, single leaves,or cut leaf pieces. For the purpose of wholehead and heart production,it is important that the leaves are wide enough to overlap and maintainhead integrity. It is also important that the core internodes andpetioles are short enough to give a closed base. The closed base andoverlapping head leaves reduce the product surface resulting in lesswilting and a longer shelf life. This is desired by traders, retailers,and consumers.

Texture appreciation is an integral part of the eating experience formany consumers. The attributes of crispness and crunch are often linkedto freshness, taste and quality perception of a particular food.Physical processes such as cutting, cooking, drying, freezing andstorage may have a significant impact on texture, leading to a loss ofcrispness and crunch in vegetables, and an alteration in taste and shelflife. Of the leafy vegetables, cos and iceberg type lettuces are prizedamongst consumers for their crispness. This attribute may be reducedduring food preparations that for example involve heat, or tissue damageas a result of processing.

Citation or identification of any document in this application is not anadmission that such document is available as prior art to the presentinvention.

SUMMARY OF THE INVENTION

There exists a need, therefore, for a cos lettuce variety which exhibitsa combination of traits including resistance to downy mildew (Bremialactucae) races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25,Bl:28-Bl:30, resistance to currant-lettuce aphid (Nasonovia ribisnigri)biotype Nr:0, resistance to Lettuce Mosaic Virus (LMV) race LMV:1, aswell as very thick mature leaves and a small head size.

The present invention addresses this need by providing a new type oflettuce (Lactuca sativa) variety, designated 41-342 RZ. Lettuce cultivar41-342 RZ exhibits a combination of traits including resistance to downymildew (Bremia lactucae) races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22,Bl:24, Bl:25, Bl:28-Bl:30, resistance to currant-lettuce aphid(Nasonovia ribisnigri) biotype Nr:0, resistance to Lettuce Mosaic Virus(LMV) race LMV:1, as well as very thick mature leaves and a small headsize.

The present invention provides seeds of lettuce cultivar 41-342 RZ,which have been deposited with the National Collections of Industrial,Marine and Food Bacteria (NCIMB) in Bucksburn, Aberdeen AB21 9YA,Scotland, UK and have been assigned NCIMB Accession No. 42410.

In one embodiment, the invention provides a lettuce plant designated41-342 RZ, representative seed of which have been deposited under NCIMBAccession No. 42410, wherein said lettuce plant may comprise acombination of traits including resistance to downy mildew (Bremialactucae) races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25,Bl:28-Bl:30, resistance to currant-lettuce aphid (Nasonovia ribisnigri)biotype Nr:0, resistance to Lettuce Mosaic Virus (LMV) race LMV:1, aswell as very thick mature leaves and a small head size.

In one embodiment, the invention provides a lettuce plant designated41-342 RZ which may exhibit a combination of traits including resistanceto downy mildew (Bremia lactucae) races Bl:1 to Bl:12, Bl:17, Bl:18,Bl:22, Bl:24, Bl:25, Bl:28-Bl:30, resistance to currant-lettuce aphid(Nasonovia ribisnigri) biotype Nr:0, resistance to Lettuce Mosaic Virus(LMV) race LMV:1, resistance to Fusarium (Fusarium oxysporum f. sp.lactucae) race Fol:1, as well as very thick mature leaves and a smallhead size, representative seed of which have been deposited under NCIMBAccession No. 42410.

In one embodiment, the invention provides a lettuce plant designated41-342 RZ, representative seed of which have been deposited under NCIMBAccession No. 42410.

In one embodiment, the invention provides for a lettuce plant which maycomprise genetic information for so exhibiting a combination of traitsincluding resistance to downy mildew (Bremia lactucae) races Bl:1 toBl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25, Bl:28-Bl:30, resistance tocurrant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, resistance toLettuce Mosaic Virus (LMV) race LMV:1, as well as very thick matureleaves and a small head size, wherein the genetic information is ascontained in a plant, representative seed of which having been depositedunder NCIMB Accession No. 42410.

In one embodiment, the invention provides for a lettuce plant exhibitinga combination of traits including resistance to downy mildew (Bremialactucae) races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25,Bl:28-Bl:30, resistance to currant-lettuce aphid (Nasonovia ribisnigri)biotype Nr:0, resistance to Lettuce Mosaic Virus (LMV) race LMV:1, aswell as very thick mature leaves and a small head size, and having thegenetic information for so exhibiting the combination of traits, whereinthe genetic information is as contained in a plant, representative seedof which having been deposited under NCIMB Accession No. 42410.

In an embodiment of the present invention, there also is provided partsof a lettuce plant of the invention, which may include parts of alettuce plant exhibiting a combination of traits including resistance todowny mildew (Bremia lactucae) races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22,Bl:24, Bl:25, Bl:28-Bl:30, resistance to currant-lettuce aphid(Nasonovia ribisnigri) biotype Nr:0, resistance to Lettuce Mosaic Virus(LMV) race LMV:1, as well as very thick mature leaves and a small headsize, or parts of a lettuce plant having any of the aforementionedresistance(s) and a combination of traits including one or moremorphological or physiological characteristics tabulated herein,including parts of lettuce variety 41-342 RZ, wherein the plant partsare involved in sexual reproduction, which include, without limitation,microspores, pollen, ovaries, ovules, embryo sacs or egg cells and/orwherein the plant parts are suitable for vegetative reproduction, whichinclude, without limitation, cuttings, roots, stems, cells orprotoplasts and/or wherein the plant parts are tissue culture ofregenerable cells in which the cells or protoplasts of the tissueculture are derived from a tissue such as, for example and withoutlimitation, leaves, pollen, embryos, cotyledon, hypocotyls, meristematiccells, roots, root tips, anthers, flowers, seeds or stems. The plants ofthe invention from which such parts may come from include those whereinrepresentative seed of which has been deposited under NCIMB AccessionNo. 42410 or lettuce variety or cultivar designated 41-342 RZ, as wellas seed from such a plant, plant parts of such a plant (such as thosementioned herein) and plants from such seed and/or progeny of such aplant, advantageously progeny exhibiting such combination of suchtraits, each of which, is within the scope of the invention; and suchcombination of traits.

In another embodiment there is a plant grown from seeds, representativeseed of which having been deposited under NCIMB Accession No. 42410.

In a further embodiment there is a plant regenerated from theabove-described plant parts or regenerated from the above-describedtissue culture. Advantageously such a plant may have morphologicaland/or physiological characteristics of lettuce variety 41-342 RZ and/orof a plant grown from seed, representative seed of which having beendeposited under NCIMB Accession No. 42410—including without limitationsuch plants having all of the morphological and physiologicalcharacteristics of lettuce variety 41-342 RZ and/or of plant grown fromseed, representative seed of which having been deposited under NCIMBAccession No. 42410. Advantageously, such a plant demonstrates thetraits of resistance to downy mildew (Bremia lactucae) races Bl:1 toBl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25, Bl:28-Bl:30, resistance tocurrant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, resistance toLettuce Mosaic Virus (LMV) race LMV:1, as well as very thick matureleaves and a small head size.

Accordingly, in still a further embodiment, there is provided a lettuceplant having all of the morphological and physiological characteristicsof lettuce variety 41-342 RZ, representative seed of which having beendeposited under NCIMB Accession No. 42410. Such a plant may be grownfrom the seeds, regenerated from the above-described plant parts, orregenerated from the above-described tissue culture. A lettuce planthaving any of the aforementioned resistance(s), and one or moremorphological or physiological characteristics recited or tabulatedherein, and a lettuce plant advantageously having all of theaforementioned resistances and the characteristics recited and tabulatedherein, are preferred. Parts of such plants—such as those plant partsabove-mentioned—are encompassed by the invention.

In one embodiment, there is provided a method for producing a progeny oflettuce cultivar 41-342 RZ which may comprise crossing a plantdesignated 41-342 RZ with itself or with another lettuce plant,harvesting the resultant seed, and growing said seed.

In a further embodiment there is provided a progeny plant produced bysexual or vegetative reproduction, grown from seeds, regenerated fromthe above-described plant parts, or regenerated from the above-describedtissue culture of the lettuce cultivar or a progeny plant thereof,representative seed of which having been deposited under NCIMB AccessionNo. 42410. The progeny may have any of the aforementioned resistance(s),and one or more morphological or physiological characteristics recitedor tabulated herein, and a progeny plant advantageously having all ofthe aforementioned resistances and the characteristics recited andtabulated herein, are preferred. Advantageously, the progeny demonstratethe traits of resistance to downy mildew (Bremia lactucae) races Bl:1 toBl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25, Bl:28-Bl:30, resistance tocurrant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, resistance toLettuce Mosaic Virus (LMV) race LMV:1, as well as very thick matureleaves and a small head size.

Progeny of the lettuce variety 41-342 RZ may be modified in one or moreother characteristics, in which the modification is a result of, forexample and without limitation, mutagenesis or transformation with atransgene.

In still another embodiment, the present invention provides progeny oflettuce cultivar 41-342 RZ produced by sexual or vegetativereproduction, grown from seeds, regenerated from the above-describedplant parts, or regenerated from the above-described tissue culture ofthe lettuce cultivar or a progeny plant thereof, in which theregenerated plant shows a combination of traits including resistance todowny mildew (Bremia lactucae) races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22,Bl:24, Bl:25, Bl:28-Bl:30, resistance to currant-lettuce aphid(Nasonovia ribisnigri) biotype Nr:0, resistance to Lettuce Mosaic Virus(LMV) race LMV:1, as well as very thick mature leaves and a small headsize.

In still a further embodiment, the invention provides a method ofproducing a hybrid lettuce seed which may comprise crossing a firstparent lettuce plant with a second parent lettuce plant and harvestingthe resultant hybrid lettuce seed, in which the first parent lettuceplant or the second parent lettuce plant may be a lettuce plant of theinvention, e.g. a lettuce plant having a combination of traits includingresistance to downy mildew (Bremia lactucae) races Bl:1 to Bl:12, Bl:17,Bl:18, Bl:22, Bl:24, Bl:25, Bl:28-Bl:30, resistance to currant-lettuceaphid (Nasonovia ribisnigri) biotype Nr:0, resistance to Lettuce MosaicVirus (LMV) race LMV:1, as well as very thick mature leaves and a smallhead size and one or more morphological or physiological characteristicstabulated herein, including a lettuce plant of lettuce cultivar 41-342RZ, representative seed of which having been deposited under NCIMB42410.

In another embodiment, the invention provides producing a lettuce plantwhich may exhibit a combination of traits including resistance to downymildew (Bremia lactucae) races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22,Bl:24, Bl:25, Bl:28-Bl:30, resistance to currant-lettuce aphid(Nasonovia ribisnigri) biotype Nr:0, resistance to Lettuce Mosaic Virus(LMV) race LMV:1, as well as very thick mature leaves and a small headsize which may comprise: crossing a mother lettuce plant with a fatherlettuce plant to produce a hybrid seed; growing said hybrid seed toproduce a hybrid plant; selfing said hybrid plant to produce F2 progenyseed; growing said F2 progeny seed to produce F2-plants; selecting saidF2-plants for exhibiting a combination of traits including resistance todowny mildew (Bremia lactucae) races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22,Bl:24, Bl:25, Bl:28-Bl:30, resistance to currant-lettuce aphid(Nasonovia ribisnigri) biotype Nr:0, resistance to Lettuce Mosaic Virus(LMV) race LMV:1, as well as very thick mature leaves and a small headsize.

Advantageously the selfing and selection may be repeated; for example atleast once, or at least twice, thrice, four times, five times, six timesor more, to produce F3 or F4 or F5 or F6 or subsequent progeny,especially as progeny from F2 may exhibit the aforementioned combinationof traits, and may be desirable.

In still a further embodiment, the invention provides a method ofproducing a lettuce cultivar which may exhibit a combination of traitsincluding resistance to downy mildew (Bremia lactucae) races Bl:1 toBl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25, Bl:28-Bl:30, resistance tocurrant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, resistance toLettuce Mosaic Virus (LMV) race LMV:1, as well as very thick matureleaves and a small head size.

The invention even further relates to a method of producing lettucewhich may comprise: (a) cultivating to the vegetative plant stage aplant of lettuce variety 41-342 RZ, representative seed of which havingbeen deposited under NCIMB Accession No. 42410, and (b) harvestinglettuce leaves or heads from the plant. The invention furthercomprehends packaging and/or processing the lettuce plants, heads orleaves.

Accordingly, it is an object of the invention to not encompass withinthe invention any previously known product, process of making theproduct, or method of using the product such that Applicants reserve theright and hereby disclose a disclaimer of any previously known product,process, or method. It is further noted that the invention does notintend to encompass within the scope of the invention any product,process, or making of the product or method of using the product, whichdoes not meet the written description and enablement requirements of theUSPTO (35 U.S.C. §112, first paragraph) or the EPO (Article 83 of theEPC), such that Applicants reserve the right and hereby disclose adisclaimer of any previously described product, process of making theproduct, or method of using the product. It may be advantageous in thepractice of the invention to be in compliance with Art. 53(c) EPC andRule 28(b) and (c) EPC. Nothing herein is to be construed as a promise.

It is noted that in this disclosure and particularly in the claimsand/or paragraphs, terms such as “comprises”, “comprised”, “comprising”and the like can have the meaning attributed to it in U.S. Patent law;e.g., they can mean “includes”, “included”, “including”, and the like;and that terms such as “consisting essentially of” and “consistsessentially of” have the meaning ascribed to them in U.S. Patent law,e.g., they allow for elements not explicitly recited, but excludeelements that are found in the prior art or that affect a basic or novelcharacteristic of the invention.

These and other embodiments are disclosed or are obvious from andencompassed by the following Detailed Description.

Deposit

The Deposit with NCIMB Ltd, Ferguson Building, Craibstone Estate,Bucksburn, Aberdeen AB21 9YA, UK, on May, 14, 2015, under depositaccession number NCIMB 42410 was made pursuant to the terms of theBudapest Treaty. Upon issuance of a patent, all restrictions upon thedeposit will be removed, and the deposit is intended to meet therequirements of 37 CFR §1.801-1.809. The deposit will be irrevocably andwithout restriction or condition released to the public upon theissuance of a patent. The deposit will be maintained in the depositoryfor a period of 30 years, or 5 years after the last request, or for theeffective life of the patent, whichever is longer, and will be replacedif necessary during that period.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description, given by way of example, but notintended to limit the invention solely to the specific embodimentsdescribed, may best be understood in conjunction with the accompanyingdrawings, in which:

FIG. 1 is an illustration of six different shapes of the fourth leaffrom a 20-day old seedling grown under optimal conditions.

FIG. 2 is a picture of the shape of the fourth leaf of 41-342 RZ.

FIG. 3 is a picture of the shape of a mature leaf of 41-342 RZ.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides methods and compositions relating to plants,seeds and derivatives of a new lettuce variety herein referred to aslettuce variety 41-342 RZ. Lettuce variety 41-342 RZ is a uniform andstable line, distinct from other such lines.

In a preferred embodiment, the specific type of breeding method employedfor developing a lettuce cultivar is pedigree selection, where bothsingle plant selection and mass selection practices are employed.Pedigree selection, also known as the “Vilmorin system of selection,” isdescribed in Fehr, W., Principles of Cultivar Development, Volume I,MacMillan Publishing Co., which is hereby incorporated by reference.

When pedigree selection is applied, in general selection is firstpracticed among F₂ plants. In the next season, the most desirable F₃lines are first identified, and then desirable F₃ plants within eachline are selected. The following season and in all subsequentgenerations of inbreeding, the most desirable families are identifiedfirst, then desirable lines within the selected families are chosen, andfinally desirable plants within selected lines are harvestedindividually. A family refers to lines that were derived from plantsselected from the same progeny from the preceding generation.

Using this pedigree method, two parents may be crossed using anemasculated female and a pollen donor (male) to produce F₁ offspring.Lettuce is an obligate self-pollination species, which means that pollenis shed before stigma emergence, assuring 100% self-fertilization.Therefore, in order to optimize crossing, a method of misting may beused to wash the pollen off prior to fertilization to assure crossing orhybridization.

Parental varieties are selected from commercial varieties thatindividually exhibit one or more desired phenotypes. Additionally, anybreeding method involving selection of plants for the desired phenotypemay be used in the method of the present invention.

The F₁ may be self-pollinated to produce a segregating F₂ generation.Individual plants may then be selected which represent the desiredphenotype in each generation (F₃, F₄, F₅, etc.) until the traits arehomozygous or fixed within a breeding population.

A detailed description of the development of lettuce variety 41-342 RZis described in Table 1. The seedlot in year 5-6, seedlot 14R.4073, wasdeposited with the NCIMB under deposit number NCIMB 42410.

TABLE 1 Year Description Location 0 Final F1-cross plants 08M.81283 ×08M.81280 Murcia, Spain in glass house. 0-1 F1 plant grown for F2 seedproduction Valencia, Spain 1 F2 plant selected in open field, followedby F3 Fijnaart, The seed production. Netherlands 2 F3 plant selected inopen field, followed by F4 Murcia, Spain seed production 2 F4 plantselected in open field, followed by F5 Murcia, Spain seed production. 3F5 plant selected in open field, followed by F6 Fijnaart, The seedproduction. Netherlands 4 F6 plant selected in open field, followed byF7 Murcia, Spain seed production. 5 F7 plant selected in open field,followed by F8 Murcia, Spain seed production. 5-6 F8 line establisheduniform, multiplied in plastic Daylesford, tunnel: seedlot 14R.4073.Australia

In one embodiment, a plant of the invention has all the morphologicaland physiological characteristics of lettuce variety 41-342 RZ. Thesecharacteristics of a lettuce plant of the invention, e.g. variety 41-342RZ, are summarized in Tables 2 and 3.

Next to the morphological and physiological characteristics, a plant ofthe invention also exhibits resistance to downy mildew (Bremia lactucaeRegel.).

As used herein resistance against Bremia lactucae is defined as theability of a plant to resist infection by each of the various strainsBl:1 to Bl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25, Bl:28 to Bl:30 ofBremia lactucae Regel. in all stages between the seedling stage and theharvestable plant stage. Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22, Bl:24,Bl:25, Bl:28 to Bl:30 means strains NL1, NL2, NL4, NL5, NL6, NL7, NL10,NL12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25, Bl:28, Bl:29, Bl:30 (VanEttekoven K, Van der Arend A J M, 1999. identification and denominationof ‘new’ races of Bremia lactucae. In: Lebeda A, Kristkova E (eds.)Eucarpia leafy vegetables '99. Palacky University, Olomouc, CzechRepublic, 1999: 171-175; Van der Arend, A. J. M., Gautier, J., Guenard,M., Michel, H., Moreau, B., de Ruijter, J., Schut, J. W. and de Witte,I. (2003). Identification and denomination of ‘new’ races of Bremialactucae in Europe by IBEB until 2002. In: Eucarpia leafy vegetables2003. Proceedings of the Eucarpia Meeting on leafy vegetables geneticsand breeding. Noorwijkerhout, The Netherlands. Eds. Van Hintum T.,Lebeda A., Pink D., Schut J. pp 151-160; Van der Arend A J M, Gautier J,Grimault V, Kraan P, Van der Laan R, Mazet J, Michel H, Schut J W,Smilde D, De Witte I (2006) Identification and denomination of “new”races of Bremia lactucae in Europe by IBEB until 2006; incorporatedherein by reference; Plantum NL (Dutch association for breeding, tissueculture, production and trade of seeds and young plants), IBEB pressrelease, “New race of Bremia lactucae Bl:27 identified and nominated”,May 2010; Plantum NL (Dutch association for breeding, tissue culture,production and trade of seeds and young plants), IBEB press release,“New race of Bremia lactucae Bl:28 identified and nominated”, March2011; Plantum NL (Dutch association for breeding, tissue culture,production and trade of seeds and young plants), IBEB press release,“New races of Bremia lactucae, Bl:29, Bl:30 and Bl:31 identified andnominated”, August 2013).

Resistance typically is tested by two interchangeable methods, describedby Bonnier, F. J. M. et al. (Euphytica, 61(3):203-211, 1992;incorporated herein by reference). One method involves inoculating 7-dayold seedlings, and observing sporulation 10 to 14 days later. The othermethod involves inoculating leaf discs with a diameter of 18 mm obtainedfrom a non-senescent, fully grown true leaf and observing sporulation 10days later.

As used herein, resistance against Nasonovia ribisnigri (Mosley), orcurrant-lettuce aphid, is defined as the plant characteristic whichresults in a non-feeding response of the aphid on the leaves of theplant in all stages between 5 true-leaf stage and harvestable plantstage (U.S. Pat. No. 5,977,443 to Jansen, J. P. A., “Aphid Resistance inComposites,” p. 12, 1999; incorporated herein by reference).

Resistance is tested by spreading at least ten aphids of biotype Nr:0 ona plant in a plant stage between 5 true leaves and harvestable stage,and observing the density of the aphid population on the plant as wellas the growth reduction after 14 days in a greenhouse, with temperaturesettings of 23 degrees Celsius in daytime and 21 degrees Celsius atnight. Day length is kept at 18 hours by assimilation lights.

As used herein, resistance against lettuce mosaic virus (LMV) may bedefined as the ability of the plant to grow normally after LMV infectionand to inhibit the virus transmission to seed. Resistance may be testedby mechanical inoculation of young plants in a climate cell orgreenhouse, as described by Pink, D. A. C. et al. (Plant Pathology,41(1): 5-12, 1992), incorporated herein by reference. Inoculatedresistant plants grow just as well as uninoculated plants and show nochlorosis or mosaic symptoms. The LMV isolate, which may be used fortesting, is Ls-1 (International Union for the Protection of NewVarieties of Plants [UPOV], Guidelines for the conduct of tests fordistinctness, uniformity and stability; 30 lettuce (Lactuca sativa L.),2002, p. 35; incorporated herein by reference).

As used herein, resistance against Fusarium oxysporum f. sp. lactucae,is defined as the ability of a plant to resist infection by race Fol:1.Resistance may be tested by two interchangeable methods. One method isdescribed by Hubbard and Gerik (1993, Plant Disease 77(7): 750-754;incorporated herein by reference). The other test is described byTsuchiya et al., (2004, J. Japan. Soc. Hort. Sci 73(2): 105-113;incorporated herein by reference).

As used herein, a very thick leaf is characterized by a thick, crispyleaf texture. For comparison the standard variety Crunchita RZ (41-101RZ) may be used. As used herein, a thick leaf is characterized by athick, slightly tough leaf texture. For comparison the standard varietyParris Island may be used. 41-342 RZ has very thick mature leaves.

As used herein, a small head size is a mature, regular-shaped head whichis comparable or similar in size to a head of the standard variety RalphRZ (41-144 RZ), both grown under long-day outdoor conditions at alatitude of 52°, i.e. sowing 100 days before the longest day, in anOceanic climate (Köppen-classification: Cfb; McKnight & Hess, 2000.Physical Geography: A Landscape Appreciation. Upper Saddle River, N.J.:Prentice Hall). The head size of plants of lettuce variety 41-342 RZ isscored as small.

As used herein, cos lettuce is Lactuca sativa L. var. longifolia Lam;also known as romaine lettuce. The plant develops in an upright open orupright compact growing habit with coarse textured, non-flabellateleaves. The younger leaves are longer than they are wide, fifteencupping together to form an elongated loose head. Leaf margins are oftenentire or undulated, rarely frilled. Outer leaves range in color fromlight green to dark green. Inner heart leaves are smaller and range fromlight yellow to light green in color.

Embodiments of the inventions advantageously have one or more, and mostadvantageously all, of these characteristics.

In Table 2, the seed color, cotyledon shape and characteristics of thefourth leaf of 41-342 RZ are compared with Ralph RZ and Verde degliortolani.

TABLE 2 Verde degli Character 41-342 RZ Ralph RZ ortolani Plant Type Cosor Cos or Cos or Romaine Romaine Romaine Seed Color White White WhiteCotyledon Shape Intermediate to Intermediate Intermediate to spatulatespatulate Shape of Fourth Leaf Elongated Elongated Elongated Rolling ofFourth Present Present Present Leaf Cupping of Fourth Uncupped UncuppedUncupped Leaf Fourth Leaf Apical Entire Entire Entire Margin Fourth LeafBasal Moderately Moderately Moderately Margin dentate dentate dentateUndulation Flat Flat Flat Green color Medium green Medium green Mediumgreen Anthocyanin Absent Absent Absent distribution

In Table 3, the mature leaf and head characteristics of 41-342 RZ arecompared with

Ralph RZ and Verde degli ortolani. RHS=Royal Horticultural Society colorchart code.

TABLE 3 Verde degli Character 41-342 RZ Ralph RZ ortolani Leaf ColorDark green Medium green Medium green to medium to dark green to darkgreen green Anthocyanin Absent Absent Absent Distribution MarginIncision Absent/shallow Absent/shallow Absent/shallow Depth MarginIndentation Entire Entire Entire Undulations of the Absent/slightAbsent/slight Absent/slight Apical Margin Leaf Size Small Small MediumLeaf Glossiness Dull Moderate Dull to moderate Leaf Blistering ModerateStrong Strong to moderate Leaf Thickness Very thick Intermediate toIntermediate thick Trichomes Absent Absent Absent Head Shape ElongateSpherical to Elongate elongate Butt Shape Rounded Rounded Rounded MidribModerately Moderately Prominently raised raised raised

In an embodiment, the invention relates to lettuce plants that have allthe morphological and physiological characteristics of the invention andhave acquired said characteristics by introduction of the geneticinformation that is responsible for the characteristics from a suitablesource, either by conventional breeding, or genetic modification, inparticular by cisgenesis or transgenesis. Cisgenesis is geneticmodification of plants with a natural gene, coding for an (agricultural)trait, from the crop plant itself or from a sexually compatible donorplant. Transgenesis is genetic modification of a plant with a gene froma non-crossable species or a synthetic gene.

Just as useful traits that may be introduced by backcrossing, usefultraits may be introduced directly into the plant of the invention, beinga plant of lettuce variety 41-342 RZ, by genetic transformationtechniques; and, such plants of lettuce variety 41-342 RZ that haveadditional genetic information introduced into the genome or thatexpress additional traits by having the DNA coding there for introducedinto the genome via transformation techniques, are within the ambit ofthe invention, as well as uses of such plants, and the making of suchplants.

Genetic transformation may therefore be used to insert a selectedtransgene into the plant of the invention, being a plant of lettucevariety 41-342 RZ or may, alternatively, be used for the preparation oftransgenes which may be introduced by backcrossing. Methods for thetransformation of plants, including lettuce, are well known to those ofskill in the art.

Vectors used for the transformation of lettuce cells are not limited solong as the vector may express an inserted DNA in the cells. Forexample, vectors which may comprise promoters for constitutive geneexpression in lettuce cells (e.g., cauliflower mosaic virus 35Spromoter) and promoters inducible by exogenous stimuli may be used.Examples of suitable vectors include pBI binary vector. The “lettucecell” into which the vector is to be introduced includes various formsof lettuce cells, such as cultured cell suspensions, protoplasts, leafsections, and callus. A vector may be introduced into lettuce cells byknown methods, such as the polyethylene glycol method, polycationmethod, electroporation, Agrobacterium-mediated transfer, particlebombardment and direct DNA uptake by protoplasts. To effecttransformation by electroporation, one may employ either friabletissues, such as a suspension culture of cells or embryogenic callus oralternatively one may transform immature embryos or other organizedtissue directly. In this technique, one would partially degrade the cellwalls of the chosen cells by exposing them to pectin-degrading enzymes(pectolyases) or mechanically wound tissues in a controlled manner.

A particularly efficient method for delivering transforming DNA segmentsto plant cells is microprojectile bombardment. In this method, particlesare coated with nucleic acids and delivered into cells by a propellingforce. Exemplary particles include those which may be comprised oftungsten, platinum, and preferably, gold. For the bombardment, cells insuspension are concentrated on filters or solid culture medium.Alternatively, immature embryos or other target cells may be arranged onsolid culture medium. The cells to be bombarded are positioned at anappropriate distance below the macroprojectile stopping plate. Anillustrative embodiment of a method for delivering DNA into plant cellsby acceleration is the Biolistics Particle Delivery System, which may beused to propel particles coated with DNA or cells through a screen, suchas a stainless steel or Nytex screen, onto a surface covered with targetlettuce cells. The screen disperses the particles so that they are notdelivered to the recipient cells in large aggregates. It is believedthat a screen intervening between the projectile apparatus and the cellsto be bombarded reduces the size of projectiles aggregate and maycontribute to a higher frequency of transformation by reducing thedamage inflicted on the recipient cells by projectiles that are toolarge. Microprojectile bombardment techniques are widely applicable, andmay be used to transform virtually any plant species, including a plantof lettuce variety 41-342 RZ.

Agrobacterium-mediated transfer is another widely applicable system forintroducing gene loci into plant cells. An advantage of the technique isthat DNA may be introduced into whole plant tissues, thereby bypassingthe need for regeneration of an intact plant from a protoplast.Agrobacterium transformation vectors are capable of replication in E.coli as well as Agrobacterium, allowing for convenient manipulations.Moreover, advances in vectors for Agrobacterium-mediated gene transferhave improved the arrangement of genes and restriction sites in thevectors to facilitate the construction of vectors capable of expressingvarious polypeptide coding genes. The vectors have convenientmulti-linker regions flanked by a promoter and a polyadenylation sitefor direct expression of inserted polypeptide coding genes.Additionally, Agrobacterium containing both armed and disarmed Ti genesmay be used for transformation. In those plant strains whereAgrobacterium-mediated transformation is efficient, it is the method ofchoice because of the facile and defined nature of the gene locustransfer. The use of Agrobacterium-mediated plant integrating vectors tointroduce DNA into plant cells, including lettuce plant cells, is wellknown in the art (See, e.g., U.S. Pat. Nos. 7,250,560 and 5,563,055).

Transformation of plant protoplasts also may be achieved using methodsbased on calcium phosphate precipitation, polyethylene glycol treatment,electroporation, and combinations of these treatments.

A number of promoters have utility for plant gene expression for anygene of interest including but not limited to selectable markers,scoreable markers, genes for pest tolerance, disease resistance,nutritional enhancements and any other gene of agronomic interest.Examples of constitutive promoters useful for lettuce plant geneexpression include, but are not limited to, the cauliflower mosaic virus(CaMV) P-35S promoter, a tandemly duplicated version of the CaMV 35Spromoter, the enhanced 35S promoter (P-e35S), the nopaline synthasepromoter, the octopine synthase promoter, the figwort mosaic virus(P-FMV) promoter (see U.S. Pat. No. 5,378,619), an enhanced version ofthe FMV promoter (P-eFMV) where the promoter sequence of P-FMV isduplicated in tandem, the cauliflower mosaic virus 19S promoter, asugarcane bacilliform virus promoter, a commelina yellow mottle viruspromoter, the promoter for the thylakoid membrane proteins from lettuce(psaD, psaF, psaE, PC, FNR, atpC, atpD, cab, rbcS) (see U.S. Pat. No.7,161,061), the CAB-1 promoter from lettuce (see U.S. Pat. No.7,663,027), the promoter from maize prolamin seed storage protein (seeU.S. Pat. No. 7,119,255), and other plant DNA virus promoters known toexpress in plant cells. A variety of plant gene promoters that areregulated in response to environmental, hormonal, chemical, and/ordevelopmental signals may be used for expression of an operably linkedgene in plant cells, including promoters regulated by (1) heat, (2)light (e.g., pea rbcS-3A promoter, maize rbcS promoter, or chlorophylla/b-binding protein promoter), (3) hormones, such as abscisic acid, (4)wounding (e.g., wunl, or (5) chemicals such as methyl jasmonate,salicylic acid, or Safener. It may also be advantageous to employorgan-specific promoters.

Exemplary nucleic acids which may be introduced to the lettuce varietyof this invention include, for example, DNA sequences or genes fromanother species, or even genes or sequences which originate with or arepresent in lettuce species, but are incorporated into recipient cells bygenetic engineering methods rather than classical reproduction orbreeding techniques. However, the term “exogenous” is also intended torefer to genes that are not normally present in the cell beingtransformed, or perhaps simply not present in the form, structure, etc.,as found in the transforming DNA segment or gene, or genes which arenormally present and that one desires to express in a manner thatdiffers from the natural expression pattern, e.g., to over-express.Thus, the term “exogenous” gene or DNA is intended to refer to any geneor DNA segment that is introduced into a recipient cell, regardless ofwhether a similar gene may already be present in such a cell. The typeof DNA included in the exogenous DNA may include DNA which is alreadypresent in the plant cell, DNA from another plant, DNA from a differentorganism, or a DNA generated externally, such as a DNA sequencecontaining an antisense message of a gene, or a DNA sequence encoding asynthetic or modified version of a gene.

Many hundreds if not thousands of different genes are known and couldpotentially be introduced into a plant of lettuce variety 41-342 RZ.Non-limiting examples of particular genes and corresponding phenotypesone may choose to introduce into a lettuce plant include one or moregenes for insect tolerance, pest tolerance such as genes for fungaldisease control, herbicide tolerance, and genes for quality improvementssuch as yield, nutritional enhancements, environmental or stresstolerances, or any desirable changes in plant physiology, growth,development, morphology or plant product(s).

Alternatively, the DNA coding sequences may affect these phenotypes byencoding a non-translatable RNA molecule that causes the targetedinhibition of expression of an endogenous gene, for example viaantisense- or cosuppression-mediated mechanisms. The RNA could also be acatalytic RNA molecule (i.e., a ribozyme) engineered to cleave a desiredendogenous mRNA product. Thus, any gene which produces a protein or mRNAwhich expresses a phenotype or morphology change of interest is usefulfor the practice of the present invention. (See also U.S. Pat. No.7,576,262, “Modified gene-silencing RNA and uses thereof.”)

U.S. Pat. Nos. 7,230,158, 7,122,720, 7,081,363, 6,734,341, 6,503,732,6,392,121, 6,087,560, 5,981,181, 5,977,060, 5,608,146, 5,516,667, eachof which, and all documents cited therein are hereby incorporated hereinby reference, consistent with the above INCORPORATION BY REFERENCEsection, are additionally cited as examples of U.S. Patents that mayconcern transformed lettuce and/or methods of transforming lettuce orlettuce plant cells, and techniques from these US Patents, as well aspromoters, vectors, etc., may be employed in the practice of thisinvention to introduce exogenous nucleic acid sequence(s) into a plantof lettuce variety 41-342 RZ (or cells thereof), and exemplify someexogenous nucleic acid sequence(s) which may be introduced into a plantof lettuce variety 41-342 RZ (or cells thereof) of the invention, aswell as techniques, promoters, vectors etc., to thereby obtain furtherplants of lettuce variety 41-342 RZ, plant parts and cells, seeds, otherpropagation material harvestable parts of these plants, etc. of theinvention, e.g. tissue culture, including a cell or protoplast, such asan embryo, meristem, cotyledon, pollen, leaf, anther, root, root tip,pistil, flower, seed or stalk.

The invention further relates to propagation material for producingplants of the invention. Such propagation material may comprise interalia seeds of the claimed plant and parts of the plant that are involvedin sexual reproduction. Such parts are for example selected from thegroup consisting of seeds, microspores, pollen, ovaries, ovules, embryosacs and egg cells. In addition, the invention relates to propagationmaterial which may comprise parts of the plant that are suitable forvegetative reproduction, for example cuttings, roots, stems, cells,protoplasts.

According to a further aspect thereof the propagation material of theinvention may comprise a tissue culture of the claimed plant. The tissueculture may comprise regenerable cells. Such tissue culture may bederived from leaves, pollen, embryos, cotyledon, hypocotyls,meristematic cells, roots, root tips, anthers, flowers, seeds and stems.(See generally U.S. Pat. No. 7,041,876 on lettuce being recognized as aplant that may be regenerated from cultured cells or tissue).

Also, the invention comprehends methods for producing a seed of a“41-342 RZ”-derived lettuce plant which may comprise (a) crossing aplant of lettuce variety 41-342 RZ, representative seed of which havingbeen deposited under NCIMB Accession No. 42410, with a second lettuceplant, and (b) whereby seed of a 41-342 RZ-derived lettuce plant form.Such a method may further comprise (c) crossing a plant grown from41-342 RZ-derived lettuce seed with itself or with a second lettuceplant to yield additional 41-342 RZ-derived lettuce seed, (d) growingthe additional 41-342 RZ-derived lettuce seed of step (c) to yieldadditional 41-342 RZ-derived lettuce plants, and (e) repeating thecrossing and growing of steps (c) and (d) for an additional 3-10generations to further generate 41-342 RZ-derived lettuce plants.

The invention further relates to the above methods that may furthercomprise selecting at steps b), d), and e), a 41-342 RZ-derived lettuceplant, exhibiting a combination of traits including resistance to downymildew (Bremia lactucae) races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22,Bl:24, Bl:25, Bl:28-Bl:30, resistance to currant-lettuce aphid(Nasonovia ribisnigri) biotype Nr:0, resistance to Lettuce Mosaic Virus(LMV) race LMV:1, as well as very thick mature leaves and a small headsize.

In particular, the invention relates to methods for producing a seed ofa 41-342 RZ-derived lettuce plant which may comprise (a) crossing aplant of lettuce variety 41-342 RZ, representative seed of which havingbeen deposited under NCIMB Accession No. 42410, with a second lettuceplant and (b) whereby seed of a 41-342 RZ-derived lettuce plant forms,wherein such a method may further comprise (c) crossing a plant grownfrom 41-342 RZ-derived lettuce seed with itself or with a second lettuceplant to yield additional 41-342 RZ-derived lettuce seed, (d) growingthe additional 41-342 RZ-derived lettuce seed of step (c) to yieldadditional 41-342 RZ-derived lettuce plants and selecting plantsexhibiting a combination of the traits including resistance to downymildew (Bremia lactucae) races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22,Bl:24, Bl:25, Bl:28-Bl:30, resistance to currant-lettuce aphid(Nasonovia ribisnigri) biotype Nr:0, resistance to Lettuce Mosaic Virus(LMV) race LMV:1, as well as very thick mature leaves and a small headsize, and (e) repeating the crossing and growing of steps (c) and (d)for an additional 3-10 generations to further generate 41-342 RZ-derivedlettuce plants that exhibit a combination of traits including resistanceto downy mildew (Bremia lactucae) races Bl:1 to Bl:12, Bl:17, Bl:18,Bl:22, Bl:24, Bl:25, Bl:28-Bl:30, resistance to currant-lettuce aphid(Nasonovia ribisnigri) biotype Nr:0, resistance to Lettuce Mosaic Virus(LMV) race LMV:1, as well as very thick mature leaves and a small headsize.

The invention additionally provides a method of introducing a desiredtrait into a plant of lettuce variety 41-342 RZ which may comprise: (a)crossing a plant of lettuce variety 41-342 RZ, representative seed ofwhich having been deposited under NCIMB Accession No. 42410, with asecond lettuce plant that may comprise a desired trait to produce F1progeny; (b) selecting an F1 progeny that may comprise the desiredtrait; (c) crossing the selected F1 progeny with a plant of lettucevariety 41-342 RZ, to produce backcross progeny; (d) selecting backcrossprogeny which may comprise the desired trait and the physiological andmorphological characteristic of a plant of lettuce variety 41-342 RZ;and, optionally, (e) repeating steps (c) and (d) one or more times insuccession to produce selected fourth or higher backcross progeny thatmay comprise the desired trait and all of the physiological andmorphological characteristics of a plant of lettuce variety 41-342 RZ,when grown in the same environmental conditions. The invention, ofcourse, includes a lettuce plant produced by this method.

Backcrossing may also be used to improve an inbred plant. Backcrossingtransfers a specific desirable trait from one inbred or non-inbredsource to an inbred that lacks that trait. This may be accomplished, forexample, by first crossing a superior inbred (A) (recurrent parent) to adonor inbred (non-recurrent parent), which carries the appropriate locusor loci for the trait in question. The progeny of this cross are thenmated back to the superior recurrent parent (A) followed by selection inthe resultant progeny for the desired trait to be transferred from thenon-recurrent parent. After five or more backcross generations withselection for the desired trait, the progeny are heterozygous for locicontrolling the characteristic being transferred, but are like thesuperior parent for most or almost all other loci. The last backcrossgeneration would be selfed to give pure breeding progeny for the traitbeing transferred. When a plant of lettuce variety 41-342 RZ,representative seed of which having been deposited under NCIMB AccessionNo. 42410, is used in backcrossing, offspring retaining the combinationof traits including resistance to downy mildew (Bremia lactucae) racesBl:1 to Bl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25, Bl:28-Bl:30,resistance to currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0,resistance to Lettuce Mosaic Virus (LMV) race LMV:1, as well as verythick mature leaves and a small head size are progeny within the ambitof the invention. Backcrossing methods may be used with the presentinvention to improve or introduce a characteristic into a plant of theinvention, being a plant of lettuce variety 41-342 RZ. See, e.g., U.S.Pat. No. 7,705,206 (incorporated herein by reference consistent with theabove INCORPORATION BY REFERENCE section), for a general discussionrelating to backcrossing.

The invention further involves a method of determining the genotype of aplant of lettuce variety 41-342 RZ, representative seed of which hasbeen deposited under NCIMB Accession No. 42410, or a first generationprogeny thereof, which may comprise obtaining a sample of nucleic acidsfrom said plant and detecting in said nucleic acids a plurality ofpolymorphisms. This method may additionally comprise the step of storingthe results of detecting the plurality of polymorphisms on a computerreadable medium. The plurality of polymorphisms is indicative of and/orgive rise to the expression of the morphological and physiologicalcharacteristics of lettuce variety 41-342 RZ.

There are various ways of obtaining genotype data from a nucleic acidsample. Genotype data may be gathered which is specific for certainphenotypic traits (e.g. gene sequences), but also patterns of randomgenetic variation may be obtained to construct a so-called DNAfingerprint. Depending on the technique used a fingerprint may beobtained that is unique for lettuce variety 41-342 RZ. Obtaining aunique DNA fingerprint depends on the genetic variation present in avariety and the sensitivity of the fingerprinting technique. A techniqueknown in the art to provide a good fingerprint profile is called AFLPfingerprinting technique (See generally U.S. Pat. No. 5,874,215), butthere are many other marker based techniques, such as RFLP (orRestriction fragment length polymorphism), SSLP (or Simple sequencelength polymorphism), RAPD (or Random amplification of polymorphic DNA)VNTR (or Variable number tandem repeat), Microsatellite polymorphism,SSR (or Simple sequence repeat), STR (or Short tandem repeat), SFP (orSingle feature polymorphism) DArT (or Diversity Arrays Technology), RADmarkers (or Restriction site associated DNA markers) (e.g. Baird et al.PloS One Vol. 3 e3376, 2008; Semagn et al. African Journal ofBiotechnology Vol. 5 number 25 pp. 2540-2568, 29 Dec. 2006). Nowadays,sequence-based methods are utilizing Single Nucleotide Polymorphisms(SNPs) that are randomly distributed across genomes, as a common toolfor genotyping (e.g. Elshire et al. PloS One Vol. 6: e19379, 2011;Poland et al. PloS One Vol. 7: e32253; Truong et al. PLoS One Vol. 7number 5: e37565, 2012).

With any of the aforementioned genotyping techniques, polymorphisms maybe detected when the genotype and/or sequence of the plant of interestis compared to the genotype and/or sequence of one or more referenceplants. As used herein, the genotype and/or sequence of a referenceplant may be derived from, but is not limited to, any one of thefollowing: parental lines, closely related plant varieties or species,complete genome sequence of a related plant variety or species, or thede novo assembled genome sequence of one or more related plant varietiesor species. For example, it is possible to detect polymorphisms for thecharacteristic of downy mildew resistance by comparing the genotypeand/or the sequence of lettuce variety 41-342 RZ with the genotypeand/or the sequence of one or more reference plants. The referenceplant(s) used for comparison in this example may for example be, but isnot limited to, any of the comparison varieties Crunchita RZ or RalphRZ.

The polymorphism revealed by these techniques may be used to establishlinks between genotype and phenotype. The polymorphisms may thus be usedto predict or identify certain phenotypic characteristics, individuals,or even species. The polymorphisms are generally called markers. It iscommon practice for the skilled artisan to apply molecular DNAtechniques for generating polymorphisms and creating markers.

The polymorphisms of this invention may be provided in a variety ofmediums to facilitate use, e.g. a database or computer readable medium,which may also contain descriptive annotations in a form that allows askilled artisan to examine or query the polymorphisms and obtain usefulinformation.

As used herein “database” refers to any representation of retrievablecollected data including computer files such as text files, databasefiles, spreadsheet files and image files, printed tabulations andgraphical representations and combinations of digital and image datacollections. In a preferred aspect of the invention, “database” refersto a memory system that may store computer searchable information.

As used herein, “computer readable media” refers to any medium that maybe read and accessed directly by a computer. Such media include, but arenot limited to: magnetic storage media, such as floppy discs, hard disc,storage medium and magnetic tape; optical storage media such as CD-ROM;electrical storage media such as RAM, DRAM, SRAM, SDRAM, ROM; and PROMs(EPROM, EEPROM, Flash EPROM), and hybrids of these categories such asmagnetic/optical storage media. A skilled artisan may readily appreciatehow any of the presently known computer readable mediums may be used tocreate a manufacture which may comprise computer readable medium havingrecorded thereon a polymorphism of the present invention.

As used herein, “recorded” refers to the result of a process for storinginformation in a retrievable database or computer readable medium. Forinstance, a skilled artisan may readily adopt any of the presently knownmethods for recording information on computer readable medium togenerate media which may comprise the polymorphisms of the presentinvention. A variety of data storage structures are available to askilled artisan for creating a computer readable medium where the choiceof the data storage structure will generally be based on the meanschosen to access the stored information. In addition, a variety of dataprocessor programs and formats may be used to store the polymorphisms ofthe present invention on computer readable medium.

The present invention further provides systems, particularlycomputer-based systems, which contain the polymorphisms describedherein. Such systems are designed to identify the polymorphisms of thisinvention. As used herein, “a computer-based system” refers to thehardware, software and memory used to analyze the polymorphisms. Askilled artisan may readily appreciate that any one of the currentlyavailable computer-based system are suitable for use in the presentinvention.

Lettuce leaves are sold in packaged form, including without limitationas pre-packaged lettuce salad or as lettuce heads. Mention is made ofU.S. Pat. No. 5,523,136, incorporated herein by reference consistentwith the above INCORPORATION BY REFERENCE section, which providespackaging film, and packages from such packaging film, including suchpackaging containing leafy produce, and methods for making and usingsuch packaging film and packages, which are suitable for use with thelettuce leaves of the invention. Thus, the invention comprehends the useof and methods for making and using the leaves of the lettuce plant ofthe invention, as well as leaves of lettuce plants derived from theinvention. The invention further relates to a container which maycomprise one or more plants of the invention, or one or more lettuceplants derived from a plant of the invention, in a growth substrate forharvest of leaves from the plant in a domestic environment. This way theconsumer may pick very fresh leaves for use in salads. More generally,the invention includes one or more plants of the invention or one ormore plants derived from lettuce of the invention, wherein the plant isin a ready-to-harvest condition, including with the consumer picking hisown, and further including a container which may comprise one or more ofthese plants.

The invention is further described by the following numbered paragraphs:

1. A lettuce plant designated 41-342 RZ, representative seed of whichhaving been deposited under NCIMB Accession No. 42410, wherein saidplant comprises at least the following combination of traits includingresistance to downy mildew (Bremia lactucae) races Bl:1 to Bl:12, Bl:17,Bl:18, Bl:22, Bl:24, Bl:25, Bl:28-Bl:30, resistance to currant-lettuceaphid (Nasonovia ribisnigri) biotype Nr:0, resistance to Lettuce MosaicVirus (LMV) race LMV:1, as well as very thick mature leaves and a smallhead size.

2. The lettuce plant of paragraph 1 wherein the plant has resistance toFusarium (Fusarium oxysporum f. sp. lactucae) race Fol:1.

3. A seed of the plant of paragraph 1.

4. A part of the plant of paragraph 1, wherein said part of the plant issuitable for sexual reproduction.

5. The part of the plant of paragraph 4, wherein said part comprises amicrospore, pollen, an ovary, an ovule, an embryo sac or an egg cell.

6. A part of the plant of paragraph 1, wherein said part of the plant issuitable for vegetative reproduction.

7. The part of paragraph 6, wherein said part comprises a cutting, aroot, a stem, a cell or a protoplast.

8. A tissue culture of regenerable cells or protoplasts from the lettuceplant of paragraph 1.

9. The tissue culture of paragraph 8, wherein said cells or protoplastsof the tissue culture which are derived from a from leaf, pollen, anembryo, a cotyledon, a hypocotyl, a meristematic cell, a root, a roottip, an anther, a flower, a seed or a stem.

10. A method for producing a progeny plant of a lettuce plant ofparagraph 1, comprising crossing the plant of paragraph 1 with itself orwith another lettuce plant, harvesting the resultant seed, and growingsaid seed.

11. A progeny plant produced by the method of paragraph 10, wherein saidprogeny exhibits a combination of traits including resistance to downymildew (Bremia lactucae) races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22,Bl:24, Bl:25, Bl:28-Bl:30, resistance to currant-lettuce aphid(Nasonovia ribisnigri) biotype Nr:0, resistance to Lettuce Mosaic Virus(LMV) race LMV:1, as well as very thick mature leaves and a small headsize.

12. A progeny plant produced by the method of paragraph 10, wherein saidprogeny plant has all the morphological and physiologicalcharacteristics of the lettuce plant designated 41-342 RZ,representative seed of which having been deposited under NCIMB AccessionNo. 42410, wherein said plant comprises at least the followingcombination of traits resistance to downy mildew (Bremia lactucae) racesBl:1 to Bl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25, Bl:28-Bl:30,resistance to currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0,resistance to Lettuce Mosaic Virus (LMV) race LMV:1, as well as verythick mature leaves and a small head size.

13. A progeny plant produced by the method of paragraph 10, wherein saidprogeny plant, representative seed of which having been deposited underNCIMB Accession NCIMB 42410, is modified in one or more othercharacteristics.

14. The progeny plant of paragraph 13, wherein the modification iseffected by mutagenesis.

15. The progeny plant of paragraph 13, wherein the modification iseffected by transformation with a transgene.

16. A method of producing a hybrid lettuce seed comprising crossing afirst parent lettuce plant with a second parent lettuce plant andharvesting the resultant hybrid lettuce seed, wherein said first parentlettuce plant or said second parent lettuce plant is the lettuce plantof paragraph 1.

17. A hybrid lettuce plant produced by the method of paragraph 16.

18. A method of producing a lettuce cultivar exhibiting a combination oftraits including resistance to downy mildew (Bremia lactucae) races Bl:1to Bl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25, Bl:28-Bl:30, resistance tocurrant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, resistance toLettuce Mosaic Virus (LMV) race LMV:1, as well as very thick matureleaves and a small head size, comprising: crossing a mother lettuceplant with a father lettuce plant to produce a hybrid seed; growing saidhybrid seed to produce a hybrid plant; selfing said hybrid plant toproduce F2 progeny seed; growing said F2 progeny seed to produceF2-plants; selecting said F2-plants for exhibiting resistance to downymildew (Bremia lactucae) races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22,Bl:24, Bl:25, Bl:28-Bl:30, resistance to currant-lettuce aphid(Nasonovia ribisnigri) biotype Nr:0, resistance to Lettuce Mosaic Virus(LMV) race LMV:1, as well as very thick mature leaves and a small headsize, and, selfing said selected F2-plants to produce F3 progeny seed;growing said F3 progeny seed to produce F3-plants; selecting F3-plantsfor exhibiting resistance to downy mildew (Bremia lactucae) races Bl:1to Bl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25, Bl:28-Bl:30, resistance tocurrant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, resistance toLettuce Mosaic Virus (LMV) race LMV:1, as well as very thick matureleaves and a small head size, optionally followed by more selfing andselection steps.

19. A lettuce cultivar produced by the method of paragraph 18.

20. A method for producing lettuce leaves as a fresh vegetablecomprising packaging leaves of a plant of paragraph 1.

21. A method for producing lettuce leaves as a processed food comprisingprocessing leaves of a plant of paragraph 1.

22. A container comprising one or more lettuce plants of paragraph 1 forharvest of leaves.

23. A lettuce plant having morphological and/or physiologicalcharacteristics of a lettuce plant, representative seed of which havingbeen deposited under NCIMB Accession No. 42410.

24. A method of introducing a desired trait into a plant of lettucevariety 41-342 RZ comprising: (a) crossing a plant of lettuce variety41-342 RZ, representative seed of which having been deposited underNCIMB Accession No. 42410, with a second lettuce plant that comprisesthe desired trait to produce F1 progeny; (b) selecting an F1 progenythat comprises the desired trait; (c) crossing the selected F1 progenywith a plant of lettuce variety 41-342 RZ, to produce backcross progenyand (d) selecting backcross progeny comprising the desired trait and thephysiological and morphological characteristic of a plant of lettucevariety 41-342 RZ, when grown in the same environmental conditions.

25. The method of paragraph 24 further comprising (e) repeating steps(c) and (d) one or more times in succession to produce selected fourthor higher backcross progeny that comprise the desired trait and all ofthe physiological and morphological characteristics of a plant oflettuce variety 41-342 RZ, when grown in the same environmentalconditions.

26. A lettuce plant produced by the method of paragraph 24 or 25.

27. A method for producing a seed of a 41-342 RZ-derived lettuce plantcomprising (a) crossing a plant of lettuce variety 41-342 RZ,representative seed of which having been deposited under NCIMB AccessionNo. 42410, with a second lettuce plant, and (b) whereby seed of a 41-342RZ-derived lettuce plant form.

28. The method of paragraph 27 further comprising (c) crossing a plantgrown from 41-342 RZ-derived lettuce seed with itself or with a secondlettuce plant to yield additional 41-342 RZ-derived lettuce seed, (d)growing the additional 41-342 RZ-derived lettuce seed of step (c) toyield additional 41-342 RZ-derived lettuce plants, and (e) repeating thecrossing and growing of steps (c) and (d) for an additional 3-10generations to generate further 41-342 RZ-derived lettuce plants.

29. The method of paragraph 27 or 28 further comprising selecting atsteps b), d), and e), a 41-342 RZ-derived lettuce plant, exhibiting acombination of traits including resistance to downy mildew (Bremialactucae) races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25,Bl:28-Bl:30, resistance to currant-lettuce aphid (Nasonovia ribisnigri)biotype Nr:0, resistance to Lettuce Mosaic Virus (LMV) race LMV:1, aswell as very thick mature leaves and a small head size.

30. A seed produced by the method of paragraph 27, 28, or 29.

31. A method of determining the genotype of a plant of lettuce variety41-342 RZ, representative seed of which has been deposited under NCIMBAccession No. 42410, or a first generation progeny thereof, comprisingobtaining a sample of nucleic acids from said plant and comparing saidnucleic acids to a sample of nucleic acids obtained from a referenceplant, and detecting a plurality of polymorphisms between the twonucleic acid samples, wherein the plurality of polymorphisms areindicative of lettuce variety 41-342 RZ and/or give rise to theexpression of any one or more, or all, of the morphological andphysiological characteristics of lettuce variety 41-342 RZ of paragraph1.

32. The method of paragraph 31 additionally comprising the step ofstoring the results of detecting the plurality of polymorphisms on acomputer readable medium, or transmitting the results of detecting theplurality of polymorphisms.

33. A lettuce plant comprising genetic information for so exhibiting acombination of traits including resistance to downy mildew (Bremialactucae) races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25,Bl:28-Bl:30, resistance to currant-lettuce aphid (Nasonovia ribisnigri)biotype Nr:0, resistance to Lettuce Mosaic Virus (LMV) race LMV:1, aswell as very thick mature leaves and a small head size, wherein thegenetic information is as contained in a plant, representative seed ofwhich having been deposited under NCIMB Accession No. 42410.

34. The lettuce plant of paragraph 33, exhibiting a combination oftraits including resistance to downy mildew (Bremia lactucae) races Bl:1to Bl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25, Bl:28-Bl:30, resistance tocurrant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, resistance toLettuce Mosaic Virus (LMV) race LMV:1, as well as very thick matureleaves and a small head size, and having the genetic information for soexhibiting the combination of traits, wherein the genetic information isas contained in a plant, representative seed of which having beendeposited under NCIMB Accession No. 42410.

35. The lettuce plant of paragraph 1, which is grown from seed havingbeen deposited under NCIMB Accession No. 42410.

36. A lettuce plant having all the morphological and physiologicalcharacteristics of the lettuce plant of paragraph 1.

37. A hybrid lettuce plant grown from the seed of paragraph 17.

Having thus described in detail preferred embodiments of the presentinvention, it is to be understood that the invention is not to belimited to particular details set forth in the above description as manyapparent variations thereof are possible without departing from thespirit or scope of the present invention.

What is claimed is:
 1. A lettuce plant designated 41-342 RZ,representative seed of which having been deposited under NCIMB AccessionNo. 42410, wherein said plant comprises at least the followingcombination of traits including resistance to downy mildew (Bremialactucae) races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25,Bl:28-Bl:30, resistance to currant-lettuce aphid (Nasonovia ribisnigri)biotype Nr:0, resistance to Lettuce Mosaic Virus (LMV) race LMV:1, aswell as very thick mature leaves and a small head size.
 2. The lettuceplant of claim 1 wherein the plant has resistance to Fusarium (Fusariumoxysporum f. sp. lactucae) race Fol:1.
 3. A seed of the plant ofclaim
 1. 4. A part of the plant of claim 1, wherein said part of theplant is suitable for sexual reproduction.
 5. The part of the plant asclaimed in claim 4, wherein said part comprises a microspore, pollen,ovary, ovule, embryo sac or egg cell.
 6. A part of the plant of claim 1,wherein said part of the plant is suitable for vegetative reproduction.7. The part as claimed in claim 6, wherein said part comprises acutting, root, stem, cell or protoplast.
 8. A tissue culture ofregenerable cells or protoplasts from the lettuce plant of claim
 1. 9.The tissue culture as claimed in claim 8, wherein said cells orprotoplasts of the tissue culture are derived from a from a tissuecomprising a leaf, pollen, embryo, cotyledon, hypocotyl, meristematiccell, root, root tip, anther, flower, seed or stem.
 10. A method forproducing a progeny plant of a lettuce plant of claim 1, comprisingcrossing the plant of claim 1 with itself or with another lettuce plant,harvesting the resultant seed, and growing said seed.
 11. A progenyplant produced by the method of claim 10, wherein said progeny exhibitsa combination of traits including resistance to downy mildew (Bremialactucae) races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25,Bl:28-Bl:30, resistance to currant-lettuce aphid (Nasonovia ribisnigri)biotype Nr:0, resistance to Lettuce Mosaic Virus (LMV) race LMV:1, aswell as very thick mature leaves and a small head size.
 12. A progenyplant produced by the method of claim 10, wherein said progeny plant hasall the morphological and physiological characteristics of the lettuceplant designated 41-342 RZ, representative seed of which having beendeposited under NCIMB Accession No. 42410, wherein said plant comprisesat least the following combination of traits resistance to downy mildew(Bremia lactucae) races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22, Bl:24,Bl:25, Bl:28-Bl:30, resistance to currant-lettuce aphid (Nasonoviaribisnigri) biotype Nr:0, resistance to Lettuce Mosaic Virus (LMV) raceLMV:1, as well as very thick mature leaves and a small head size.
 13. Aprogeny plant produced by the method of claim 10, wherein said progenyplant, representative seed of which having been deposited under NCIMBAccession NCIMB 42410, is modified in one or more other characteristics.14. The progeny plant as claimed in claim 13, wherein the modificationis effected by mutagenesis.
 15. The progeny plant as claimed in claim13, wherein the modification is effected by transformation with atransgene.
 16. A method of producing a hybrid lettuce seed comprisingcrossing a first parent lettuce plant with a second parent lettuce plantand harvesting the resultant hybrid lettuce seed, wherein said firstparent lettuce plant or said second parent lettuce plant is the lettuceplant of claim
 1. 17. A hybrid lettuce seed produced by the method ofclaim
 16. 18. A method of producing a lettuce cultivar exhibiting acombination of traits including resistance to downy mildew (Bremialactucae) races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25,Bl:28-Bl:30, resistance to currant-lettuce aphid (Nasonovia ribisnigri)biotype Nr:0, resistance to Lettuce Mosaic Virus (LMV) race LMV:1, aswell as very thick mature leaves and a small head size, comprising:crossing a mother lettuce plant with a father lettuce plant to produce ahybrid seed; growing said hybrid seed to produce a hybrid plant; selfingsaid hybrid plant to produce F2 progeny seed; growing said F2 progenyseed to produce F2-plants; selecting said F2-plants for exhibitingresistance to downy mildew (Bremia lactucae) races Bl:1 to Bl:12, Bl:17,Bl:18, Bl:22, Bl:24, Bl:25, Bl:28-Bl:30, resistance to currant-lettuceaphid (Nasonovia ribisnigri) biotype Nr:0, resistance to Lettuce MosaicVirus (LMV) race LMV:1, as well as very thick mature leaves and a smallhead size, and, selfing said selected F2-plants to produce F3 progenyseed; growing said F3 progeny seed to produce F3-plants; selectingF3-plants for exhibiting resistance to downy mildew (Bremia lactucae)races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25, Bl:28-Bl:30,resistance to currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0,resistance to Lettuce Mosaic Virus (LMV) race LMV:1, as well as verythick mature leaves and a small head size, optionally followed by moreselfing and selection steps.
 19. A lettuce cultivar produced by themethod of claim
 18. 20. A method for producing lettuce leaves as a freshvegetable comprising packaging leaves of a plant of claim
 1. 21. Amethod for producing lettuce leaves as a processed food comprisingprocessing leaves of a plant of claim
 1. 22. A container comprising oneor more lettuce plants of claim 1 for harvest of leaves.
 23. A lettuceplant having morphological and/or physiological characteristics of alettuce plant, representative seed of which having been deposited underNCIMB Accession No.
 42410. 24. A method of introducing a desired traitinto a plant of lettuce variety 41-342 RZ comprising: (a) crossing aplant of lettuce variety 41-342 RZ, representative seed of which havingbeen deposited under NCIMB Accession No. 42410, with a second lettuceplant that comprises the desired trait to produce F1 progeny; (b)selecting an F1 progeny that comprises the desired trait; (c) crossingthe selected F1 progeny with a plant of lettuce variety 41-342 RZ, toproduce backcross progeny and (d) selecting backcross progeny comprisingthe desired trait and the physiological and morphological characteristicof a plant of lettuce variety 41-342 RZ, when grown in the sameenvironmental conditions.
 25. The method of claim 24 further comprising(e) repeating steps (c) and (d) one or more times in succession toproduce selected fourth or higher backcross progeny that comprise thedesired trait and all of the physiological and morphologicalcharacteristics of a plant of lettuce variety 41-342 RZ, when grown inthe same environmental conditions.
 26. A lettuce plant produced by themethod of claim
 24. 27. A method for producing a seed of a 41-342RZ-derived lettuce plant comprising (a) crossing a plant of lettucevariety 41-342 RZ, representative seed of which having been depositedunder NCIMB Accession No. 42410, with a second lettuce plant, and (b)whereby seed of a 41-342 RZ-derived lettuce plant forms.
 28. The methodof claim 27 further comprising (c) crossing a plant grown from 41-342RZ-derived lettuce seed with itself or with a second lettuce plant toyield additional 41-342 RZ-derived lettuce seed, (d) growing theadditional 41-342 RZ-derived lettuce seed of step (c) to yieldadditional 41-342 RZ-derived lettuce plants, and (e) repeating thecrossing and growing of steps (c) and (d) for an additional 3-10generations to generate further 41-342 RZ-derived lettuce plants. 29.The method of claim 28 further comprising selecting at steps b), d), ande), a 41-342 RZ-derived lettuce plant, exhibiting a combination oftraits including resistance to downy mildew (Bremia lactucae) races Bl:1to Bl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25, Bl:28-Bl:30, resistance tocurrant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, resistance toLettuce Mosaic Virus (LMV) race LMV:1, as well as very thick matureleaves and a small head size.
 30. A seed produced by the method of claim27.
 31. A method of determining the genotype of a plant of lettucevariety 41-342 RZ, representative seed of which has been deposited underNCIMB Accession No. 42410, or a first generation progeny thereof,comprising obtaining a sample of nucleic acids from said plant andcomparing said nucleic acids to a sample of nucleic acids obtained froma reference plant, and detecting a plurality of polymorphisms betweenthe two nucleic acid samples, wherein the plurality of polymorphisms areindicative of lettuce variety 41-342 RZ and/or give rise to theexpression of any one or more, or all, of the morphological andphysiological characteristics of lettuce variety 41-342 RZ as claimed inclaim
 1. 32. The method of claim 31 additionally comprising the step ofstoring the results of detecting the plurality of polymorphisms on acomputer readable medium, or transmitting the results of detecting theplurality of polymorphisms.
 33. A lettuce plant comprising geneticinformation for so exhibiting a combination of traits includingresistance to downy mildew (Bremia lactucae) races Bl:1 to Bl:12, Bl:17,Bl:18, Bl:22, Bl:24, Bl:25, Bl:28-Bl:30, resistance to currant-lettuceaphid (Nasonovia ribisnigri) biotype Nr:0, resistance to Lettuce MosaicVirus (LMV) race LMV:1, as well as very thick mature leaves and a smallhead size, wherein the genetic information is as contained in a plant,representative seed of which having been deposited under NCIMB AccessionNo.
 42410. 34. The lettuce plant as claimed in claim 33, exhibiting acombination of traits including resistance to downy mildew (Bremialactucae) races Bl:1 to Bl:12, Bl:17, Bl:18, Bl:22, Bl:24, Bl:25,Bl:28-Bl:30, resistance to currant-lettuce aphid (Nasonovia ribisnigri)biotype Nr:0, resistance to Lettuce Mosaic Virus (LMV) race LMV:1, aswell as very thick mature leaves and a small head size, and having thegenetic information for so exhibiting the combination of traits, whereinthe genetic information is as contained in a plant, representative seedof which having been deposited under NCIMB Accession No.
 42410. 35. Thelettuce plant of claim 1, which is grown from seed having been depositedunder NCIMB Accession No.
 42410. 36. A lettuce plant having all themorphological and physiological characteristics of the lettuce plant asclaimed in claim
 1. 37. A hybrid lettuce plant grown from the seed ofclaim 17.